This invention relates to storage sheds for containers, and more particularly it is concerned with a container storage shed of the type in which containers are placed on and removed from shelves by means of a crane.
In, for example, U.S. Pat. No. 3,543,952, a container storage shed is proposed wherein shelves, having a plurality of container storing zones arranged vertically and horizontally are equipped with a movable crane including an elevating member provided with a truck having piston-cylinder means for vertically moving a spreader frame provided with container hitching levers for pivotal movement in a horizontal direction. The shelves have guide rails for the truck secured thereto. When it is desired to remove a container from the shelf, the crane is moved together with the elevating member to the front of the zone in which the container of interest is located. Then the truck is transferred from the elevating member to the rails, and the spreader frame is positioned above the container. Thereafter, the piston-cylinder means is actuated to move the spreader frame downwardly to a position above the container. The container hitching levers are pivotally moved and hitched on to the container, and the piston-cylinder means is actuated to lift the spreader frame to hang the container. The truck is transferred from the guide rails to the elevating member to move the container to the crane. The container is moved to its destination by the crane which travels to the destination while the elevating member is vertically moved. The process described hereinabove is reversed when the container is placed on the shelf.
In the prior art, the crane must be supported in its entirety by the shelf, so that the shelves have an increased strength and this is uneconomical. When the truck is transferred from the elevating member to the shelf, it is completely separated from the elevatory member. This raises the problem that difficulties are experienced in permitting the truck to negotiate the gap between the elevating member and to the shelf and move on to the guide rails without any trouble. The truck is subjected to high shocks when moved on to the guide rails, so that it is impossible to operate the truck at high speed. Thus, the operation of placing a container on the shelf and removing the same therefrom is timeconsuming and uneconomical. Moreover the levels for hitching a container and moving the same in a pivotal movement in a horizontal direction makes it necessary to provide the shelf with a space for moving the lever in a horizontal direction in addition to the space for moving the spreader frame in a vertical direction. This involves a low space efficiency and makes the system uneconomical because the zone for storing the container on the shelf is increased. In the layout of the prior art, the truck travels longitudinally of the crane thereby making it impossible to perform an operation of placing the container on the shelf and removing the same therefrom at high speed because it is time-consuming to position the spreader frame above the container.
In another prior art construction, a spreader frame is extended from the elevating member of the crane supported by a shelf toward the shelf to enable the spreader frame to support a container. In this system, the spreader frame is not completely separated from the elevating member, so that the disadvantage of difficult negotiation of the gap between the elevating member and the shelf is eliminated. In this prior art system, the container is supported on the spreader frame extending from the elevating member and lifted, so that a large moment of rotation would be applied to the elevating member and the spreader frame, thereby causing a high load to be applied to the crane. This is uneconomical because the crane would have to have a greatly increased strength.